Summary: A biochemical analysis was undertaken of thermosensitive mutants of 168 harbouring mutations in several genes, involved in the synthesis of the major wall teichoic acid, poly(glycerol phosphate), poly(groP). Incorporation of a pulse of [2-H]glycerol into whole cells, following shift to the restrictive growth temperature, was used to assess synthesis of this polymer and to seek evidence of accumulation of a specific precursor. The rate of incorporation into poly(groP) was strongly decreased in all mutants; glycerol uptake was diminished by 80% or more for a strain harbouring mutation (formerly ) and one bearing (formerly ). The pool of CDP-glycerol (CDP-gro), a specific precursor of poly(groP), was increased, relative to the wild-type, for all mutations except , where the pool of CDP-gro was reduced. Cytoplasmic extracts, assayed at the permissive temperature for glycerol-3-phosphate cytidylyltransferase (gro-PCT), the enzyme synthesizing CDP-gro, revealed wild-type activities for all mutations except . Gro-PCT activity in the latter strain was 100-fold lower and, unlike that in all other mutant strains, highly thermolabile. This thermosensitivity suggests that encodes gro-PCT. The identification, in a gene encoding a poly(groP)-specific enzyme, of a mutation conferring a thermosensitive growth phenotype renders explicit the conclusion that synthesis of this teichoic acid is essential for the growth of .


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